By JOHN NOBLE WILFORD
Copyright 1996 The New York Times
NEW YORK -- Another meteorite from Mars has been found to contain evidence for possible life on that planet, British scientists reported on Thursday.
American geologists, who in August first announced finding possibly life-related chemical and mineral compounds in an older Mars rock, said that the new research was "very exciting, and independent confirmation" of their own startling and controversial results. The British discovery was certain to encourage intensive testing of meteorites from Mars and increase scientific interest in new spacecraft missions to the planet, the first of which is scheduled for launching next Wednesday.
The fact that the latest evidence comes from a much younger meteorite, scientists said, indicated that some kind of life could have existed on Mars more recently than had been thought likely. Spacecraft observations of the planet's landscape strongly suggest that Mars was once a warmer and wetter planet and could have supported at least some forms of microbial life.
The British examined a meteorite, designated 79001, that crystallized 175 million years ago and was ejected from Mars, presumably by an asteroid impact, only 600,000 years ago. The previous evidence came from a potato-sized rock that crystallized about 3.6 billion years ago and was blown away from Mars 16 million years ago. Both were found on the ice of Antarctica.
"This is great," said Dr. Michael Meyer, a biologist who specializes in extraterrestrial studies at the National Aeronautics and Space Administration, in Washington. "It means we have more than one sample with hints of life. And it means Mars could have been inhabited for quite a long period and could even have some life today."
The new findings, reported in London at a meeting of the Royal Society, were the result of research by Dr. Ian Wright and Dr. Colin Pillinger, of the Open University, in Milton Keynes, England, and Dr. Monica Grady, of the Open University and the Natural History Museum, in London. Their laboratory is considered by scientists to be one of the best in the world for studying carbon in extraterrestrial materials.
The British scientists could not be reached for interviews after the meeting, but a description of their findings was included in the meeting announcement. Their analysis revealed the presence of organic compounds in the meteorite that could be associated with life. One line of evidence suggested carbon compositions that are usually formed from microbially produced methane.
Dr. Everett K. Gibson Jr., a geologist at the Johnson Space Center, in Houston, was familiar with the research and provided details in a telephone interview. He is a co-leader, with Dr. David S. McKay of the Johnson center, of the team of NASA and university scientists that made the first discovery of what they said were hydrocarbon compounds, minerals and possibly microfossils associated with primitive microbial life on Mars.
"We're pleased that the British results support our data," Gibson said, noting that they were based on a different type of analysis in a different laboratory.
After the American report was published in August in the journal Science, Gibson and his colleagues drew a skeptical response.
As Gibson described it, the British group heated samples of the meteorite to several levels of high temperature, at each step examining gases emanating from the rock. Any Earth contaminants near the surface would presumably have escaped at the lower temperatures.
In this way, the scientists identified carbon compounds in the samples with a composition that, Gibson said, "may be similar to that produced by microbial activity." The signature for this was the discovered ratio of carbon isotopes, atoms of the same element that have different numbers of neutrons in their nuclei.
At least 12 meteoritic fragments, collected by geologists in Antarctica in the 1980s, have been determined to come from Mars. The meteorite studied by the British, 79001, is considered the "Rosetta stone" of the lot, because it was the analysis of trapped gases within the rock that linked the objects to Mars. The gases were almost identical in composition to atmospheric samples gathered by the Viking spacecraft in 1976.
Definitive conclusions about the possibility of Martian life may have to wait until spacecraft bring carefully selected samples back from the planet, possibly in a decade or so. NASA is planning 10 flights of orbiting spacecraft and robotic landers to explore Mars, beginning with the launching next week of Mars Global Surveyor, a low-cost unmanned craft to study the planet's climate and geology from orbit. Another craft, designed to land on Mars, is to be launched on Dec. 2, aiming for an arrival at the planet next July 4.
AUFORA News Update Monday, December 16th, 1996
DISCOVERY SUPPORTS MARTIAN LIFE THEORY
from the Daily Telegraph Helios Science News (www.helios.org)
LONDON - The scientists who claimed last August to have found evidence of life on Mars have announced that they have strengthened their case.
One of the main criticisms of the claims, based on studies of the meteorite rock ALH 84001, was that organisms so small - only one hundredth the diameter of a human hair in length - had never been recorded on Earth.
Now US scientists led by Dr. Everett Gibson of NASA's Johnson Space Centre in Houston, Tex., in collaboration with a British team led by Prof. Colin Pillinger of the Open University, have found "nanobacteria" living two kilometres down in the basalt rock of the Columbia River Valley.
They are to present their findings in a lecture given at Gresham College in London this week. "The beautiful thing is the story appears to be holding together," Gibson said.
The team also reported evidence that the carbonates found in ALH 84001 did not contaminate it by seeping in from the Antarctic ice where the meteorite was discovered but formed on Mars 3.6 billion years ago.
Clues to past life are turning up in other rock samples from outer space. Pillinger found that several other specimens shared five or six chemical properties of ALH 84001, including evidence of organic compounds.
--------------------------------------END------------------------------------------------------- Other Places of Interest on the Web
Evidence of Primative Life From Mars http://www.jsc.nasa.gov/pao/flash
Life on Mars http://www.fas.org/mars/
Mars Introduction http://bang.lanl.gov/solarsys/mars.htm#
Center for Mars Exploration Homepage http://cmex-www.arc.nasa.gov/
Mars facts and pictures from The Nine Planets Solar System Tour, maintained by Students for the Exploration and Development of Space http://seds.lpl.arizona.edu/nineplanets/nineplanets/mars.html